A static approach towards coke collapse modelling in blast furnace

Abstract

Burden distribution control in a blast furnace has a close relationship with wind acceptance and gas utilisation. Quantification of radial distribution of ore and coke is important for proper control of blast furnace operation. Charging of metallic burden over a layer of coke causes a portion of the coke layer to get dislodged from its original position, similar to the situation observed when a heavy material is dropped on a bed of lighter particles. This phenomenon, designated 'coke collapse', significantly changes the ore/coke distribution in the radial direction and thus affects the permeability of the furnace shaft. In the present work a mathematical model for quantifying the amount of coke collapse has been proposed on the basis of 'stability of slope theory'. The calculation from this model has been compared with the results from experiments in simplified physical models. Predictions of the mathematical model are in good agreement with experimental results. List of symbolsE M formation energy of mixed bed F s factor of safety F v external force g acceleration due to gravity H vertical distance between falling point of ore and the burden surface at the furnace centre DL c increase of coke layer thickness in the centre M charged mass of ore in one dump N r normal component of the reaction to gravity P n normal force, act on the side of the nth slice r radius of potential failure surface R reaction to gravity T r tangential component of the reaction to gravity T n shearing force, act on the side of the nth slice V component of ore velocity in the direction of coke surface W n weight of a slice a n Angle between the normal component of reaction to gravity and vertical direction s normal stress t f shear strength of the soil t d shear stress developed along the potential failure surface w angle of internal friction

Review on Modeling and Simulation of Blast Furnace

“…It also provides the basic boundary information to study the burden descent and associated phenomena in the BF body. For a long time, such prediction has mainly relied on the models derived from the motion of a single particle or particle assembly . In recent years, the DEM approach, which considers all individual particles and their interaction with each other, has become a promising tool to guide burden charging operation …”

“…For a long time, such prediction has mainly relied on the models derived from the motion of a single particle or particle assembly. [121][122][123][124] In recent years, the DEM approach, which considers all individual particles and their interaction with each other, has become a promising tool to guide burden charging operation. [79,125] Figure 11 shows a representative application of DEM in simulating the bell-less charging system mainly used in modern BFs.…”

Numerical Investigation of Burden Distribution in a Blast Furnace

“…In the past decades, substantial experiments and numerical studies have been conducted, focusing on various aspects of burden distribution, including falling trajectory of burden materials from the charging device onto the burden surface, development of the burden profile at the throat, coke collapse towards the center of the furnace under the influence of ore charging onto the coke layer, size segregation, descent of burden layers, and shaft thermal conditions relevant to heat transfer behavior and gas distribution . In particular, the discrete element method (DEM) is a typical approach which can capture motions of individual particles, hence particle flow behavior.…”

“…In particular, the discrete element method (DEM) is a typical approach which can capture motions of individual particles, hence particle flow behavior. Such an approach has been extensively used to study burden distribution phenomena . For example, Ho et al investigated the effects of different parameters on gouge formation, and showed that burden distribution is affected by particle density, size, chute angle, and distance between the bin and chute.…”

Investigation of Coke Collapse in the Blast Furnace Using Mathematical Modeling and Small Scale Experiments

“…This is a complication as the profile may vary strongly depending on the charging program. Some authors [17][18][19] have utilized the stability theory of slopes to determine if a layer would be stable upon charging a pellet layer. This is based on stability theory used extensively in geological applications and dam constructions.…”